Muskrats collected in a stream in Emmet Co., Michigan were naturally infected with Wardius zibethicus. Helisoma antrosa collected from this locality shed cercariae of W. zibethicus in the laboratory. Rediae and cercariae from these snails are described. Comparative measurements are given for a similar species of paramphistome cercaria. The cercariae demonstrated both positive phototaxis and emergence periodicity. Green vegetation was preferred as an encystment site. Incomplete development of the adult stage was attained in hamsters, white mice, a deer mouse, and guinea pigs.